This study is a comprehensive epidemiologic investigation into the relationship between serum triglyceride (TG) levels and coronary heart disease (CHD), based on recently published theoretical and empirical advances. There are three components to this investigation: 1) an analysis of several existing cardiovascular databases for evidence of a significant association between CHD and specific lipid interactions involving TG; 2) an analysis of these databases to investigate the role of measurement precision on the association between elevated TG levels and CHD; and 3) a survey of both expert lipidologists and community clinicians to examine current practices related to screening for and treatment of elevated TG levels for the purpose of reducing CHD risk. Commitments have been obtained from the investigators responsible for five databases to be used in the first two components of this study. These data sets include those of the Lipid Research Clinics Prevalence and Mortality Follow-up Studies; the Lipid Research Clinics Coronary Primary Prevention Trial; the Multiple Risk Factor Intervention Trial; the National Heart, Lung, and Blood Type II Coronary Intervention Study; and the Coronary Drug Project. For the first component, detailed statistical analyses of all databases will be performed, specifically examining the role of lipid interactions involving TG and their association with CHD. For the second component, more precise estimates of each subject's lipid levels will be recalculated using the multiple lipid measurements already available in each database. Each dataset will then be analyzed for evidence of an independent relationship between TG and CHD and to validate the theoretical findings suggesting that measurement imprecision may explain the difficulty of detecting an independent TG-CHD association. The public health implications of the current state of knowledge surrounding TG will be assessed with survey research techniques in the third component. The results of this investigation will shed substantial light on the controversial relationship between TG and CHD, a topic of great importance to preventive cardiology. Additionally, important methodological information will be obtained in the study of interactions and precision of variables in epidemiologic analysis.